<!DOCTYPE html>
<html>

<head>
    <style>
        .father {
            display: flex;
            justify-content: center;
            align-items: center;
            width: 500px;
            height: 500px;
            background-color: antiquewhite;
        }

        .container {
            width: 200px;
            height: 200px;
            background-color: rgb(9, 131, 238);
        }

        .son {
            width: 100px;
            height: 100px;
            background-color: lightpink;
        }
    </style>
</head>

<body>
    <div class="father">
        <!-- 添加一个容器包裹son -->
        <div class="container">
            <span class="son">son</span>
        </div>
    </div>
</body>

</html>